Israeli Prime Minister Benjamin Netanyahu said that Israel was preparing to pull out of UNESCO, the UN's cultural and educational agency, hours after the United States made a similar announcement.

The Israeli leader called the US decision to exit UNESCO "brave and moral", according to a statement.

The statement added that Mr Netanyahu had instructed his Foreign Ministry to begin preparations for leaving the organisation as well.

The US announced its withdrawal from UNESCO complaining about how it is run and about what Washington described as bias against Israel.

"This decision was not taken lightly, and reflects US concerns with mounting arrears at UNESCO, the need for fundamental reform in the organisation, and continuing anti-Israel bias," State Department spokeswoman Heather Nauert said in a statement.

The withdrawals are a severe blow for the Paris-based organisation which began work in 1946 and is known for designating World Heritage sites such as the ancient city of Palmyra in Syria and Sceilig Mhichíl in Co Kerry.

Under UNESCO rules, the withdrawal will become effective as of the end of December 2018.

Until that time, the United States, which provides around $80 million to UNESCO annually, will remain a full member.

The organisation, which employs around 2,000 people worldwide, most of them based in Paris, has long been the object of criticism over its use of resources and resolutions that have been perceived by Israel and other countries as biased.

Director-General Irina Bokova expressed disappointment at the US decision.

"At the time when conflicts continue to tear apart societies across the world, it is deeply regrettable for the United States to withdraw from the United Nations agency promoting education for peace and protecting culture under attack," she said.

"This is a loss to the United Nations family. This is a loss for multilateralism."

UNESCO is in the process of selecting a new chief, whose priority will be to revive its fortunes.

The US move underscores the scepticism expressed by President Donald Trump about the need for the United States to remain engaged in multi-lateral bodies.

Mr Trump has touted an "America First" policy, which puts US economic and nationalist interests ahead of international commitments.

Diplomats expressed concern about the loss of US engagement.

"The absence of the United States or any large country with a lot of power is a loss. It's not just about money, it's promoting ideals that are vital to countries like the United States, such as education and culture," a UNESCO-based diplomat said.